One such inspection machine is already in use, on which a rotary conveyor operating with a driven endless conveying mechanism and a facing stationary friction surface is arranged on the inward conveyor some distance ahead of the intermediate conveyor, within the operating range of the single lateral inspection device. This known inspection machine, which is compact in its construction, makes it possible for bottles or the like to be checked for dirt, flaws, etc. both in the base area and in the side wall area. The bottles are transferred in a secure upright position to the onward conveyor by the conveying mechanisms of the intermediate conveyor, which are being driven at the same speed. However, it is a drawback that the rotary conveyor is only able to act on the bottles in their lowermost wall area, so as not to overly restrict the field of view of the lateral inspection device. Since, moreover, a large angle of rotation is required over a relatively short transfer distance, the transportation of the bottles in the region of the rotary conveyor is extremely unstable and the results of the inspection fail to meet the standard required. Besides, it is very easy for the bottles to fall over before they are intercepted by the intermediate conveyor once they have negotiated the rotary conveyor. The known inspection machine is therefore unsuitable for high throughput levels.
Also in use is an inspection machine having an inward conveyor, an outward conveyor arranged at a distance therefrom and an intermediate conveyor which transfers rotationally symmetrical bottles between the inward and outward conveyors. On this inspection machine a first lateral inspection device is arranged on the inward conveyor, a second lateral inspection device on the outward conveyor and a base inspection device in the area of the gap between the inward and the outward conveyors. The intermediate conveyor features two endless conveyor mechanisms which act on opposite sides of the bottles and are driven at different speeds, and which turn the bottles through a certain angle on their way from the inward conveyor to the outward conveyor. The bottles are therefore turning as the intermediate conveyor hands them over to the outward conveyor, and they can easily be set spinning and topple over. This results in damage to the second lateral inspection device and serious disruptions to production. Furthermore, the fact that the bottles are independently rotating in the region of the base inspection device can disrupt the operation of the latter.